Grahams Gas Law

GAS LAWS

KINETIC ENERGY/ GRAHAM'S LAW LAB

Chemistry

Block 8

April 20th, 2005

Purpose:

To observe how masses of atoms and molecules affect their rate of diffusion, and explain our observations in terms of mass, velocity, kinetic energy and temperature.

Warm-up Question:

1. What is the definition of temperature?

Temperature is a measure of the average Kinetic Energy of the particles composing a material.

2. What is the definition of diffusion?

Diffusion is a spontaneous spreading of particles until they are uniformly distributed in their container.

3. If we increase the temperature of sample of gas, then what about the gas molecules will have to change?

The gas molecules would begin to increase in speed since the temperature would increase.

4. The element iodine (I2) diffuses more slowly than ethanol (CH3CH2CH2OH). Why is this?

Iodine is heavier in atomic mass then ethanol, slowing down its process to diffuse. Iodine weighs 253.6u while ethanol weighs 60.03u, giving ethanol a faster diffusions rate.

Procedure A:

1. Obtain a glass tube and wash it with water. Dry the outside of the tube with a paper towel. Next, squirt some acetone into the tube. A small amount is all that is needed. Then dry the inside of the tube by passing air through the tube (use a fan, the window, blow through it, etc.)

2. Use chalk to label one end of your lab station, "HC1," and the other end, "NH3."

3. Lay the glass tube on the table and place the thermometer on the table next to the tube.

4. !!!CATION!!! THE NH3 AND THE HCI ARE IN VERY CONCENTRATED FORMS. DO NOT ALLOW EITHER CHEMICAL TO COME INTO CONTACT WITH YOUR SKIN. IF THE NH3 OR HCl SPILLS, GET A DAMP PAPER TOWEL AND CLEAN IT UP IMMEDIATELY!!!

5. Obtain 1 small bottle of HCI and 1 small bottle of NH3. Place each bottle in their respective ends of the lab table. Obtain forceps, label them, "HC1" or "NH3"with tape, and place them at their respective end of the lab table.

6. Record the temperature of the air around the tube in the data table.

7. Separate the cotton ball into pieces small enough to stuff into the ends of the glass tube. Do not put them into the tube yet.

8. While holding the cotton ball with the forceps, place 4 drops of HCl or NH3 (whichever corresponds to the label on the forceps).

9. Repeat step 8 with the other chemical. You should now have two small cotton balls, one with 7 drops of HCI, one with 7 drops of NH3. Keep them at their respective ends of the lab station.

10. Record the time in minutes and seconds.

11. Using the forceps, insert each ball into its respective end of the tube. Do not shove them all the way in - leave a bit hanging out so that you can remove it from the tube when necessary.

12. Observe the tube for a smoke ring to appear. When it does, record the following:

a. The time taken for the smoke ring to appear.

b. The distance (in cm) that the ring was from each cotton ball.

13. Remove the cotton balls from the tube, and dispose of each in the appropriate container.

14. Clean out the tube as in step 1.

Procedure B:

1. This set up is the same as in procedure A but a heat lamp is used to warm the tube. Set the lamp up so that it is shining over the entire tube and thermometer.

2. Record the temperature.

3. Repeat steps 1 -13 from procedure A.

Procedure C:

1. This set up is the same as in A and B, except ice .is used to cool the tube. Obtain a tray with ice in it, cover the ice with a layer of paper towel, place the tube and the thermometer on the ice, and after it has had time to cool, record the temperature of the tube and its surroundings.

2. Record the temperature.

3. Repeat steps 1 - 13 from procedure A.

Data:

Procedure A Procedure B Procedure C

Temperature 25 C 57 C 0 C

Time taken for ring to form 70 seconds 65 seconds 120 seconds

Distance from NH3 12 cm 13.5 cm 13 cm

Distance from HCl 14 cm 13 cm 12.6 cm

Follow-up Questions:

1. Rank the three procedures in terms of time from fastest to slowest to form the ring.

Fastest - B

Middle - A

Slowest - C

2. In procedure B, the temperature of the gases should have been higher that in procedures A and C. Refer to warm-up question #1 and rank the three procedures in terms of kinetic energy from highest to lowest.

Highest - B

Middle - A

Lowest - C

3. What two properties of the particles of a gas are responsible for its kinetic energy?

The two properties of the particles of a gas that are responsible for its kinetic energy are mass and velocity.

4. Which